WO2016128336A1

WO2016128336A1 - Exhaust gas pipe with deformed sub-region

Info

Publication number: WO2016128336A1
Application number: PCT/EP2016/052587
Authority: WO
Inventors: Dominik Rödel; Frank Kimmel; Reiner Helbig
Original assignee: Tenneco Gmbh
Priority date: 2015-02-11
Filing date: 2016-02-08
Publication date: 2016-08-18
Also published as: DE102015101980A1

Abstract

The invention relates to an exhaust gas pipe (1) for a motor vehicle, comprising a first sub-region (T1) with a length (a1) and a second sub-region (T2) with a length (a2). The first sub-region (T1) has a cross-sectional profile (Q1), and the second sub-region (T2) has a cross-sectional profile (Q2) which deviates from the circular shape. The cross-sectional profile (Q2), when described in a Cartesian coordinate system, has four segments (S1, S2, S3, S4), each of which extends over 90°. The points (P) of each segment (S1, S2, S3, S4) of the cross-sectional profile (Q2) with the coordinates x, y satisfy the following condition: (x/a)ⁿ+ (y/b)ⁿ = 1, with 20 ≥ n ≥ 2, the exponent n can be different for each segment (S1, S2, S3, S4), or each segment (S1, S2, S3, S4) is composed of at least three circular portions, a corner circular portion (KE), a base circular portion (KB), and a lateral circular portion (KS); adjacent circular portions (KE-KB, KE-KS) of a segment (S1, S2, S3, S4) have different radii (RE, RB, RS), where RE < RB and RE < RS; in each segment (S1, S2, S3, S4), the ratio RE/RB, RE/RS of the radius (RE) to the next largest radius (RB, RS) is maximally as large as 1/N, where 2.5 <= N; and different radii (RE, RB, RS) can be used for different segments (S1, S2, S3, S4).

Description

- -

Exhaust pipe with deformed portion

The invention relates to an exhaust pipe for a motor vehicle having a first partial area T1 with a length al and a second partial area with a length a2, wherein the first partial area T1 has a cross-sectional profile Q1 and the second partial area T2 has a cross-sectional profile Q2 deviating from the circular shape , wherein the cross-sectional profile Q2, shown in the Cartesian coordinate system, four segments Sl, S2, S3, S4, which extend over 90 ° each.

From DE 101 58 358 AI exhaust pipes are known, which consist of several along the tube longitudinal axis arranged portions whose dimensioning is adapted to the operation of the vehicle acting on them different loads. At least one mechanically and / or thermally more heavily loaded section has a deviating from the shape of the circular cross-section profile, which in the case of higher mechanical load relative to an axis perpendicular to the operating main load level axis increased resistance moment against bending has. For the cross-sectional profile deviating from the circular cross-sectional shape, an oval or an ellipse may be considered whose long semiaxis, in the case of the higher mechanical load, runs essentially at right angles to the axis of the operational bending load.

An oval consists of two radii, which are used twice in pairs opposite each other.

There are already known exhaust pipes, which have due to the space conditions deviating from a circular cross-sectional profile flatter pipe sections. These fla- - -

Chere pipe sections are characterized by a cross-sectional profile, which has flattened or straight sections or which is formed overall oval. The oval cross-section profile was used in particular for tubes with a profile residual height of more than 80%, ie a flattening of less than 20%. Flatter cross-section profiles with a lower profile residual height have a shape deviating from the oval.

The training as an oval was made with the proviso that the larger radius of the oval is formed as small as possible, the smaller radius is even smaller. The alignment of the long semi-axis is done exclusively according to the given space conditions, ie i. d. R. horizontal. An alignment of the long semiaxis according to the direction of the higher mechanical bending load, ie vertical, therefore does not take place.

Tube cross sections with common oval or elliptical cross section are also known from DE 197 13 963 C1 and DE 42 28 188 AI.

From DE 102 00 669 AI, Fig. 3c, a pipe cross section is known, which is composed of a total of four segments, wherein the two segments are the same with the smallest radius.

Square and rectangular tube cross sections are known from WO 01/065084 AI and DE 28 21 592 AI.

The object of the invention is to design and arrange an exhaust pipe in such a way that the properties with regard to the hydraulic cross section, the strength and the acoustic properties are optimal. - -

Increasingly, conflicts arise between the available installation space on the underbody of the vehicle and the required pipe size or required pipe diameter. So that the required distances can be maintained, the circular tubes must be increasingly deformed area by area.

In the case of pipes, the hydraulic diameter of the pipes should, if possible, be reduced as little as possible by the deformation or flattening. If the hydraulic diameter is reduced or the flow resistance is increased by unfavorable profile selection, this has a negative effect on the fuel consumption of the vehicle. By flattening the tubes or their wall parts of the structure-borne noise is adversely affected. Such wall parts have an increased structure-borne sound.

By deforming the stability of the pipes and the exhaust system can also be reduced, and therefore the choice of holder positions and their number are limited.

The desired profiles should be feasible with the least possible manufacturing effort. Therefore, in pipes for the purpose of deformation of the classical pressing process, thus no IHU process or a process using a granulate filling is desired. An IHU process or a process using a granulate filling is also possible. Preferably, the inner circumference of the deformed tube or the applied cross-sectional profile and the original tube should be the same.

Deformed subregions must be inherently stable, ie they must not change the shape, for example, kinking or falling significantly, either in the process of deforming itself or in a subsequent bending process in an uncontrolled manner. - -

The object, the following condition is achieved according to the invention in that the points P of the respective segment Sl, S2, S3, S4 of the cross-sectional profile ^¬ Q2 having the coordinates x, y erf

with n_max = 2.5, 2.8, 3, 3.5, 4, 5, 6, 7, 8, 9, 10, 12 or 15, or that the respective segment Sl, S2, S3, S4 consists of min ^¬ at least three circular sections is composed of a corner circle section KE, a bottom circle section KB and a side circle section KS, wherein adjacent circular sections KE-KB, KE-KS a segment Sl, S2, S3, S4 different radii RE, RB, RS have, with RE <RB and RE <RS, wherein in the respective segment Sl, S2, S3, S4, the ratio RE / RB, RE / RS of the radius RE to the next larger radius RB, RS is at most as large as 1 / t, with 2.5 <= t <= t_max, with t_max = 10, 30, 50, 100, 200, 300, 400 or 500.

The use of cross-sectional profiles Q2, which at least in segments form a superellipse (Lavall's Oval) or a radius tripple RE, RB, RS of the type described with

There are both acoustic and mechanical advantages over tubes with an oval cross-sectional profile or tubes with an arbitrarily deformed cross-sectional profile.

When describing cross-sectional profiles, a distinction must be made between the "acoustic membrane length" and the "geometric membrane length". The acoustic membrane length refers to the length in the cross-sectional profile, which actually oscillates and is limited by two minima of the deflection. As a geometric membrane length is called the length of the portion of the cross-sectional profile, by the larger - -

Radius is defined. In comparative tests between the geometric length and the acoustic length, it was found that the geometric length has no discernible influence on the acoustic quality of the cross-sectional profile.

According to prevailing opinion, it was to be expected that an oval with the smallest possible radius acoustically has the best quality, and thus low structure-borne noise, since there are no pseudo-surface areas that act as a vibrational membrane. In addition, there are only two sections with the larger radius in an oval, which could form a pseudo-flat area proportion. The remaining sections of the cross-sectional profile are formed by the smaller radius.

However, in the course of development, it has been shown that the prevailing opinion is not always right. When using the cross-section profile Q2 invention, the existing corners, so the sections with the smallest radius, the stability, so that the pseudo-flat surface portions are supported with a larger radius and in sum, the tube as a whole has a better acoustic quality of the acoustics, as in the oval the case is .

In addition to this, the cross-sectional profile Q2 offers an i.d.R. the further advantage of the increased area moment of inertia. As a result, the self-supporting tube length between two holder positions can be increased and the entire structure has a higher stability.

The cross-sectional profile Q2 according to the invention is characterized by at least two radii RE and RB which are used four times over the cross section of 360 ° - -

each of the four corners once and on each of the four side faces once. The thus formed cross-sectional profile Q2 therefore has four pseudo-flat surface portions. Alternatively, deviating radii RS for the side or further radii RX, RY can be combined.

The parameters a, b are determined by the desired pipe size, such as the profile height. With a mean pipe diameter of 97 mm, for example, a = 50 and b = 40 can be selected. In principle, the parameters a, b can be different. The cross-sectional profile Q2 is then not axisymmetric to the diagonal. The parameters a, b can also be the same. The cross-section profile Q2 is then axisymmetric to the diagonal.

Experience has shown that the inventive cross-sectional profile Q2 for exhaust pipes with an inner circumference of up to 350 mm, 700 mm or a maximum of 1000 mm is advantageous. For larger exhaust pipes, no specific data is currently available. Pipes of this dimension have per se already very large radii, thus a corresponding structure-borne sound radiation. The space conditions are, as for example in marine diesel, less problematic than in motor vehicle construction, so that a need for optimization of the invention is not obvious at first. At least theoretically, however, the advantages according to the invention would also have to be achievable for such large tubes.

Against the background of different factors t and exponents n in the different quadrants of the coordinate system, the cross-sectional profile Q2 shown in the Cartesian coordinate system has to be formed neither axially nor point-symmetrically. Each quadrant is per - -

Definition for themselves as exemplified in Figures 2a, 2b shown and described.

In practice, values for t up to about 200 or for n to about 12 have proven to be advantageous. Cross sections with higher values for t or n offer the same advantages. At t> 500 or t> 15, however, the cross-sections become so angular that an inventive advantage of appreciable size is no longer expected.

It can be advantageous if the exponent n is different for the respective segment S1, S2, S3, S4 or if the respective radius RE, RB and / or RS is different for different segments S1, S2, S3, S4. Consequently, another exponent n is used for at least one of the segments S1, S2, S3, S4 than for the other segments S1, S2, S3, S4. So z. For example, the exponent n in the segment Sl may be different from the exponent n for the other segments S2-S4. The exponents n in the segments S1, S3 could also be different from the exponents n in the segments S2, S4. Thus, at least one quadrant or segment of the cross-sectional profile Q2 has a different shape.

It can be advantageous if different radii RE, RB, RS are used for different segments S1, S2, S3, S4 or if the exponent n is different for different segments S1, S2, S3, S4. Thus, for at least one of the segments S1, S2, S3, S4, another radius RE, RB or RS is used than for the other segments S1, S2, S3, S4. Accordingly, at least one of the radii RE, RB or RS differs in at least one of the segments Sl, S2, S3, S4 from the respective radius RE, RB or RS for the other segments. So z. For example, the radius RE in the segment Sl may be different from the corresponding one. radius RE in the other segments S2-S4. It would also be the radii RE, RB in the segments Sl, S3 other than the radii RE, RB in the other segments S2, S4. The combination variety is very large. Thus, at least one segment or quadrant of the cross-sectional profile Q2 with respect to at least one of the radii RE, RB, RS has a different shape than the cross-sectional profile Q2 of the remaining segments or quadrants.

Furthermore, it may be advantageous if a first derivative f of a function f is formed by removing the length of the radius R or the radii RE, RS, RB of the cross-sectional profile Q2 via the angle A (in polar coordinates) in the respective segment at an angle AI Discontinuity D and a second derivative f 'at angle AI is zero. As a rule, the function f has a maximum at the angle AI, in which the first derivative f is also zero. In contrast to an oval cross-section whose function f has a saddle point in AI. Here, the first derivative f has an extreme point (maximum) in which the second derivative is zero. On the basis of these differences, the geometry according to the invention can be measured in a simple manner.

Alternatively, a radius measurement over the circumference U is possible, so that the applied radii RE, RB, RS can be determined.

It can also be advantageous if two circular sections KB, KS have the same radius with RB = RS. At least two different radii are present, in which case both remaining radii RE, RB (or RE, RS) are used four times in the cross-sectional profile Q2 over 360 ° in each case. Alternatively, find at least three different - -

Radii RE, RB, RS Application where the radius RE is used four times and the two other radii RB, RS are used twice.

It can be advantageously provided that in addition to the circle sections KE, KB, KS one or two further circle sections KX, KY are used with a radius RX, RY, thus a total of four or five circle sections KE, KB, KS, KX, KY where the ratio 1 / t for the radius RE to the next larger radius RB, RS, RX, RY applies. Theoretically, the corner circle segment KE could be constructed over more than one corner radius RE. In this case, the smallest radius RE is decisive for the ratio 1 / t. In a corresponding manner, as already stated above, different radii RX, RY can be used for different segments S1, S2, S3, S4. The increase in the number of circular sections can be advantageous in certain cases.

Of particular importance may be for the present invention, if at least three of the circular sections KE, KB, KS, KX, KY have different radii R, such as RE, RX = RS, RB = RY. Thus, at least three different radii are used per segment S1 to S4, generally a corner radius RE, a bottom radius RB and a side radius RS, the latter two being used twice in each case opposite the corner radius RE.

In connection with the design and arrangement according to the invention, it can be advantageous if the first subregion T 1 has a circular cross-sectional profile Q 1. The preferred cross-sectional profile Ql is still round. Just - -

in exceptional cases, the entire exhaust pipe must be deformed deviating from the circular shape.

However, it is also possible to string several sub-areas with different cross-sectional profiles to each other or put in sequence so as to build a longer exhaust pipe.

It may also be advantageous if a wall thickness w is provided, wherein the wall thickness w varies over the circumference U, or if a wall thickness w is provided, wherein the wall thickness w varies in the direction of the central axis. The variation of the wall thickness substantiates further acoustic advantages, in particular with regard to special deformation measures in the connection area to further exhaust gas components.

The same is achieved by an exhaust pipe formed from a metal strip with a thickness d, wherein the thickness d is greater in an edge region B of the sheet metal strip than outside the edge region B.

It may be advantageous in general if the exhaust pipe is free of exhaust gas purification elements. The inventive avoidance of harmful structure-borne sound radiation or reduced strength comes into play only if the exhaust pipe is free of exhaust gas purification elements. For an exhaust gas purification element such as a catalyst or a filter fills the exhaust pipe and supports the pipe wall, so that the advantages of the invention are not achieved. Guiding, mixing and / or evaporator elements are not to be regarded as exhaust gas purification elements because they do not have a supporting function with respect to the pipe wall.

It may be advantageous in general if the exhaust pipe is designed as a bending pipe with only one weld. For exhaust pipes, formed from deep-drawn half shells - -

are, the benefits of the invention are also not considered. For deep-drawn half shells of the shell edge usually supports the pipe wall, so that adverse structure-borne noise is not observed.

Further advantages and details of the invention are explained in the patent claims and in the description and illustrated in the figures. Show it:

Figure 1 is a schematic diagram of an exhaust pipe with

two sections;

FIG. 2 shows a cross-sectional profile Q2 in the Cartesian coordinate system;

Figure 2a shows a partial section of Figure 2 with three

Circular sections KE to KS;

2b shows a partial section of Figure 2 with five

Circular sections KE to KY;

3a shows the representation of the first derivative of a

Function f concerning the radius of an oval cross section profile Q2;

FIG. 3b shows the first derivative f for a cross-sectional profile Q2;

Figure 4a-4g further variants of the cross-sectional profile Q2;

Figure 5 is a sectional view of the exhaust pipe with varying wall thickness w;

Figure 6 is a sectional view of a tube with varying wall thickness w; - -

Figure 7a, 7b is a sectional view of a metal strip for producing a tube with varying thickness d.

An exhaust pipe 1 according to FIG. 1 has two partial areas T1, T2, each with a length al, a2. While the partial area T1 has a cross-sectional profile Q1, the partial area T2 has a cross-sectional profile Q2 deviating therefrom. Both partial areas T1, T2 have the same central axis 1.1. While the cross-sectional profile Ql, which is formed by using two different radii, is formed oval, the cross-sectional profile Q2 is a cross-sectional profile formed from at least three different radii as described below.

According to Figure 2, the cross-sectional profile Q2 in the Cartesian coordinate system x, y is shown. The cross-sectional profile Q2 is point-symmetrical to the central axis 1.1 and is formed of several points P with the coordinates x, y. The cross-sectional profile Q2 is divided according to the division by the coordinate system into four segments S 1 to S 4, wherein each of the four segments Sl to S4 consists of three radii, the corner radius RE, the ground radius RB, and the side radius RS. All three radii RE, RS, RB are of different sizes, with the corner radius RE being the smallest radius.

According to embodiment Figure 2, the side radius RS, which in turn is smaller than the ground radius RB, by the factor t = 5.4 is greater than the corner radius RE. Since the cross-sectional profile Q2 of Figure 2 is point-symmetrical, the three other segments S2 to S4 are provided with corresponding radii. - -

The cross-sectional profile Q2 according to FIG. 2 can also be approximated to a superellipse for which the following applies

depict. In the cross section profile Q2 shown here, an exponent n = 3 is used. The further variables a, b are dependent on the size of the cross section to be selected, ie its height or width. For an exhaust pipe not shown here with a size of 97 mm, for example, the parameters a = 50 and b = 40 can be selected.

The ratio described above, ie RS = t x RE with t = 5.4, refers to the ratio of the smallest radius, ie the corner radius RE, in relation to the next larger radius, here the side radius RS. Since according to embodiment FIG. 2 the ground radius RB is made larger than the side radius RS, the ratio RE / RB between the corner radius RE and the ground radius RB is correspondingly smaller than RE / RS.

FIG. 2a shows the first quadrant of a cross-sectional profile Q2. There are also three circular sections, the corner circle section KE and the adjoining bottom circle section KB and the opposite side circle section KS, each having the aforementioned radius RE, RB, RS shown. The circular sections KB, KE, KS merge tangentially into each other and thus forms the cross-sectional profile Q2. To clarify the circle sections KB, KE, KS they are drawn at a distance from the cross-sectional profile Q2. When the geometric configuration of the cross-sectional profile Q2, the cross-sectional profile Q2 and the three circular sections KB, KE, KS are of course congruent. - 4 -

According to exemplary embodiment FIG. 2b, the segment S1 of a cross-sectional profile Q2 in the second quadrant is constructed over five circular sections KB-KS, the circular sections KX and KY being provided in addition to the three circular sections KB-KS. The circle section KX, KY is in each case placed between the two circle sections KE and KS or between the circle sections KE and KB. The respective circular sections KB - KS are assigned a respective radius RB -RS, whereby here too the corner radius RE is the smallest radius. As with embodiment 2a, at least three radii RB-RS are used, so that in addition to the smallest corner radius RE two further radii RX, RY of different sizes are used. According to embodiment 2b, the radii RB, RY, RX, RS can all differ from each other. It is also possible that the two radii RY, RX are the same size, while the two radii RB, RS are also the same size.

Accordingly, a different number and different combinations of radii RY, RX, RB, RS are possible for the different segments S 1 -S 4.

3a shows a function f is formed by removing the length of the radius R in polar coordinates of the oval cross-sectional profile Ql in the segment Sl and below a derivative f of this function f. It can be seen that the derivative f 'at an angle AI of about 50 ° has an extreme value M, which is formed as a maximum, and that in AI, the slope of the derivative f, so the second derivative f' is zero.

In contrast thereto, a pitch function f 'of a non-oval cross-sectional profile Q2 according to the invention according to FIG. 3b is shown. It points at an angle AI of approximately - -

67 ° a discontinuity D and a zero N on, where in AI at the same time the second derivative f 'is also equal to zero. The function f also has a maximum M in AI.

According to the embodiments FIGS. 4a-4f different cross-sectional profiles Q2 according to the invention are shown. All four segments Sl - S4 each have the same combination of radii RB, RE, RS, resulting in only point and axisymmetric cross-sectional profiles Q2.

The various embodiments differ in each case by the ratio of the radii used by the respective segment Sl-S4, in particular the ratio between the respectively applied corner radius RE and the next larger radius RB or RS. The ratio is indicated in the graph and varies from t = 1.4 to t = 166.6. The same cross sections according to FIGS. 4a-4f can also be mapped using an equation of the superellipse. For all these cross sections " _* ~ O

Regardless of the variables a, b, which are determined by the size of the cross-sectional profile Q2, only the exponent n varies. In FIG. 4a, n = 2 and increases by way of example to n = 10 in FIG. 4f.

Starting from Figure 4a, the cross-sectional profile Q2 is gradually edged. The size of the corner radius RE decreases gradually, while the size of the next larger radius, here RS, as well as the size of the largest radius, here RB, increases.

The exemplary embodiment according to FIG. 4g has an asymmetrical cross-sectional profile Q2 in which in each segment S1-S4 the selection and / or the combination of the different - -

Radii is different. Consequently, the factors t and the exponents n also differ.

According to Figure 5, an exhaust pipe 1 is shown with a cross-sectional profile Q2 according to the invention. In addition to the application of the cross-sectional profile Q2 according to the invention, the exhaust pipe 1 has a varying wall thickness w. The wall thickness w varies over the circumference and has its maximum in the region of a weld 1.2.

According to embodiment 6, the wall thickness w also varies. Their maximum lies in each case in an edge region B of the exhaust pipe 1, ie at the beginning and at the end of the pipe 1.

The different wall thicknesses w according to FIGS. 5 and 6 are achieved by using metal strips 2 with varying wall thickness d. The variation of the wall thickness d can be created by folding the edge regions B of the sheet metal strip 2 or by corresponding Auswalzung according to embodiment Figure 7.

The combination of the cross-sectional profile Q2 according to the invention with the application of so-called "tailored lengths", ie waisted sheets, leads to advantageous properties with regard to stability, production and vibration behavior.

- -

Reference sign list

1 exhaust pipe, pipe

1.1 central axis

1.2 weld

2 metal strips

A angle

AI angle

al length

a2 length

B edge area of 2

D discontinuity of f

d thickness of 2, wall thickness

f function

f 'derivative of f

KE corner circle section, circle section

KB ground circle section, circle section

KS side circle section, circle section

KX circle section

KY circle section

M extreme point of f, f ', maximum

N zero of f

n exponent

P point of Ql, Q2

Ql cross section profile

Q2 cross section profile

R radius

RE radius, corner radius

RB radius, ground radius

RS radius, side radius

RX radius

RY radius

Sl segment

S2 segment _ _

53 segment

54 segment

T1 subarea

T2 subarea

U scope of 1

w wall thickness

x coordinate of P

y coordinate of P

Claims

claims

1. exhaust pipe (1) for a motor vehicle having a first portion Tl with a length al and a second portion T2 with a length a2, wherein the first portion Tl has a cross-sectional profile Ql and the second portion T2 a deviating from the circular shape cross-sectional profile Q2 wherein the cross-sectional profile Q2, shown in the Cartesian coordinate system, four segments Sl, S2, S3, S4, which each extend over 90 °,

characterized ,

the points P of the respective segment S 1, S 2, S 3, S 4 of the cross-sectional profile Q 2 with the coordinates x, y satisfy the following condition: where n max ^ n> 2,

with n_max = 2.5 or 2.8 or 3 or 3.5 or 4 or 5 or 6 or 7 or 8 or 9 or 10 or 12 or 15, or that the respective segment Sl, S2, S3, S4 consists of at least three Circular sections is composed of a corner circle segment KE, a bottom circle section KB and a side circle section KS, wherein adjacent circle sections KE-KB, KE-KS of a segment Sl, S2, S3, S4 have different radii RE, RB, RS, with RE <RB and RE <RS, wherein in the respective segment Sl, S2, S3, S4 the ratio RE / RB, RE / RS of radius RE to the next larger radius RB, RS is at most equal to 1 / t, with 2.5 <= t <= t_max, with t_max = 10, 30, 50, 100, 200, 300, 400 or 500. Exhaust pipe (1) according to claim 1,

characterized ,

that for different segments Sl, S2, S3, S4 the respective radius RE, RB and / or RS is different.

Exhaust pipe (1) according to claim 1 or 2,

characterized ,

that the exponent n for different segments Sl,

S2, S3, S4 is different.

Exhaust pipe (1) according to one of the preceding claims, characterized in that

that a first derivative f of a function f formed by ablating the length of the radius R of the cross-sectional profile Q2 over the angle A at an angle AI has a tendency D and a second derivative of this function f at angle AI is zero.

that two circular sections KB, KS have the same radius RB, RS, with RB = RS.

in addition to the circular sections KE, KB, KS, one or two further circular sections KX, KY with a radius RX, RY, thus a total of four or five circular sections KE, KB, KS, KX, KY are used, the ratio 1 / t for the radius RE to the next larger radius RB, RS, RX, RY.

7. exhaust pipe (1) according to claim 6,

characterized ,

that at least three of the circular sections KE, KB, KS, KX, KY have different radii R.

8. Exhaust pipe (1) according to any one of the preceding claims, d a d u c h e c e n e c e n e,

the first partial area T1 has a circular cross-sectional profile Q1.

9. exhaust pipe (1) according to one of the preceding claims with a central axis (1.1) and a circumference U,

characterized ,

that a wall thickness w is provided, wherein the wall thickness w varies over the circumference U.

10. exhaust pipe (1) according to one of the preceding claims having a central axis (1.1) and a circumference U,

characterized ,

a wall thickness w is provided, wherein the wall thickness w varies in the direction of the central axis (1.1).

11. exhaust pipe (1) according to one of the preceding claims, formed of a sheet metal strip (2) having a thickness d, wherein the thickness d in an edge region B of the sheet metal strip (2) is greater than outside the edge region B.

12. Exhaust pipe (1) according to one of the preceding claims, d a d u c h e c e n e c e n e,

that the exhaust pipe (1) is free of exhaust gas purification elements. Exhaust pipe (1) according to one of the preceding claims, characterized in that the exhaust pipe (1) is designed as a bending tube with only one weld.